Multidimensional Construction And Strain Sensing Properties Of Graphene Ridges

Surface wrinkling,as a common phenomenon in nature,plays an important role in many aspects.Compared with the conventional etching method,the controllable fabrication of surface patterns has wider application prospects due to the advantages of low cost,simple equipment,high efficiency,and easy operation.Graphene is a two-dimensional material with excellent chemical,electrical,mechanical and optical properties.If graphene has special three-dimensional structure,it will have many interesting properties to further broaden its application aspects.Compared with graphene,graphene oxide can be more tightly bonded to the substrate due to the presence of oxygen-containing groups.Therefore,graphene oxide is commonly used to fabricate buckling patterns.In this study,we proposed a simple dimensional controlled shrinkage method to prepare reduced graphene oxide ridges.The latex balloon was used as flexible substrate and two-dimensional graphene oxide was used as coating.We pre-stretched the substrate by inflation and then uniformly coating GO onto the pre-stretched substrate by spin coating.The fabrication strain was released slowly by deflation.Due to the strain mismatch between the substrate and GO coating,graphene oxide ridges were induced and then GO was reduced by the hydrazine hydrate reduction method to obtain rGO ridges.Hierarchical reduced graphene oxide ridges based on spherical substrates are isotropic,while reduced graphene oxide ridges based on cylindrical substrates are anisotropic and oriented,especially when the cylindrical substrate is shrunk through a two-step process.If we adjust the GO concentration,we can change the thickness of the coating.As the thickness of the coating increases,the width and thickness of the ridges increase simultaneously,while as the strain is increased,the ridges thickness still increases but the width decreases,which leads to denser ridges.Through characterizing the electrical property,contact angle and solvent barrier property of reduced graphene oxide ridges,it can be seen that the ridges based on the cylindrical substrate are anisotropic in electrical property and contact angle.The reduced graphene oxide ridges are super-hydrophobic,in addition,the solvent barrier effect of graphene makes the crack-free reduced graphene oxide ridges chemically resistant,and can be directly contacted with DCM for more than 2.5 h without leakage.The strain sensing performance of reduced graphene oxide has also been studied.The sensitivity and strain sensing range,static/dynamic strain response and stability are analyzed.It is known that rGORs strain sensor has high sensitivity(maximum GF value can be ～48),wide strain sensing range(0～50%,300～530%),good static/dynamic strain response and stability.At the same time,it is also found that the strain sensitivity coefficient of the rGORs in the axial direction based on the cylindrical substrate is significantly higher than the circumferential strain sensitivity coefficient.Flexible strain sensors based on reduced graphene oxide folds can be used to detect human activity and monitor vital signs,and we have also prepared multi-functional gloves coated with rGORs,which have strain sensing properties and self-cleaning due to the surface coated with rGORs.Even after hand washing,ultrasonic,machine washing and chemical immersion treatment,rGORs can maintain the microstructure.